Technical Barriers to the Consumption of Higher Blends of Ethanol - Stephanie Searle, Francisco Posada Sanchez, Chris Malins & John German The ...
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Technical Barriers to the Consumption of Higher Blends of Ethanol Stephanie Searle, Francisco Posada Sanchez, Chris Malins & John German The International Council on Clean Transportation February 2014
DISCLAIMER
The International Council on Clean Transportation (ICCT) prepared
this paper at the request of the Bipartisan Policy Center (BPC). BPC
is releasing this paper as it was presented to us. The findings and
opinions expressed in this paper are solely those of the authors. BPC
takes no position on the findings nor conclusions developed in this
paper, and this paper does not necessarily represent the views of the
Bipartisan Policy Center, BPC staff, its founders, its board of
directors, or the RFS advisory group.
ABOUT BPC
Founded in 2007 by former Senate Majority Leaders Howard Baker,
Tom Daschle, Bob Dole and George Mitchell, the Bipartisan Policy
Center is a non-profit organization that drives principled solutions
through rigorous analysis, reasoned negotiation and respectful
dialogue. With projects in multiple issue areas, BPC combines
politically balanced policymaking with strong, proactive advocacy
and outreach.
ACKNOWLEDGEMENTS
Thanks to the Bipartisan Policy Center for funding this work, and to
Nic Lutsey and Oscar Delgado at the International Council on Clean
Transportation, and to Adam Christensen at Johns Hopkins
University for reviewing this paper and providing information.
Technical Barriers to the Consumption of Higher Blends of Ethanol
2Substantial changes in energy markets, persistent challenges in courts, and difficulties in
the implementation of relevant enacting laws have kept the Renewable Fuel Standard (RFS)
at the forefront of energy policy discussions. There are both strong advocates in support of
holding firm on the existing requirements and calls for outright repeal. But there also exists
an active middle ground focusing on reforming, not repealing, the RFS.
The Bipartisan Policy Center (BPC) is undertaking a yearlong effort aimed at fostering
constructive dialogue and action on reforming the RFS. To do this, BPC is convening a
diverse RFS advisory group to discuss opportunities for reform, hosting public workshops to
solicit broad input, and ultimately publishing viable policy options based, in part, on the
advisory group’s deliberations.
As part of this effort, BPC has commissioned a series of background papers on various RFS
topics. These papers are targeted at a broad audience that includes not only BPC’s advisory
group, but also policymakers, industry, and the public, with the intention of educating and
informing the wider debate surrounding this issue. Given a topic as complex as the RFS,
these papers cover multiple issues, providing a focused view from the perspectives of
technology, infrastructure, policy, and law. The first three background papers listed will be
released in early February. The remaining two, which are two separate law firms’
perspectives on the same topic, will be released by the end of February.
1. Technical Barriers to the Consumption of Higher Blends of Ethanol
The International Council on Clean Transportation
2. Petroleum and Renewable Fuels Supply Chain
Stillwater Associates LLC
3. Inventory of Federal Regulations Affecting Biofuels other than the
Renewable Fuel Standard
Van Ness Feldman
4. The Environmental Protection Agency’s Authority to Amend the Renewable
Fuel Standard
Sutherland Asbill & Brennan LLP
5. The Environmental Protection Agency’s Authority to Amend the Renewable
Fuel Standard
Bracewell & Giuliani LLP
BPC is releasing these papers as they were presented to us. The findings and opinions
expressed in these background papers are solely those of the author(s). BPC takes no
position on the findings nor conclusions developed in these papers, and they do not
necessarily represent the views of BPC staff or the RFS advisory group.
To read other background papers in the series or for additional information about this effort,
please visit http://bipartisanpolicy.org/projects/energy/renewable-fuel.
Technical Barriers to the Consumption of Higher Blends of Ethanol
3Table of Contents
Executive Summary ........................................................ 5
Introduction ................................................................... 10
Vehicle Compatibility ................................................... 12
Fuel Economy With Ethanol Blends ............................................................................ 12
Effects of Ethanol on Car Emissions ........................................................................... 12
Ethanol Effects on Materials and Fuel Leaks ................................................................ 15
Phase Separation of Water and Ethanol from Gasoline.................................................. 16
Flex-Fuel Vehicles (FFVs) ......................................................................................... 16
Small Engines and Off-road Applications .................. 19
Equipment With Small Gasoline Engines ..................................................................... 19
Motorcycles ............................................................................................................ 20
Aviation and Marine................................................................................................. 20
Infrastructure .................................................................. 22
Fuel Dispensers ...................................................................................................... 22
Underground Storage Tanks (USTs) ........................................................................... 23
Pipelines ................................................................................................................ 23
Timeline for Consumption of Higher Blends of
Ethanol ........................................................................... 25
Timeline for Technological Changes in Vehicles and Infrastructure ................................. 25
Ethanol Consumption Under Projections of RFS2 Implementation................................... 26
Conclusions.................................................................... 29
Summary of Technical Barriers to the Consumption of Higher Ethanol Blends .................. 29
Projections for Ethanol Consumption to 2022 .............................................................. 29
Endnotes ........................................................................ 31
Technical Barriers to the Consumption of Higher Blends of Ethanol
4Executive Summary
The U.S. Renewable Fuel Standard (RFS) mandates the consumption of biofuel in road
transport fuel. The first RFS program (RFS1) required biofuel to be blended into gasoline
over the period of 2006 to 2012. In 2007, the RFS1 was amended and extended to 2022,
becoming the RFS2. To date, most of the RFS2 biofuel mandate has been fulfilled with
ethanol, which is now typically blended into gasoline at a 10 percent mixture by volume
(E10). Given stagnating demand for gasoline due to rising fuel economy in the nation’s fleet
and other factors, further increases to U.S. ethanol consumption would require the use of
higher blends of ethanol, either in “normal” vehicles or in flex-fuel vehicles (FFVs) designed
to tolerate blends of up to 85 percent ethanol (E85).
This study reviews technical barriers to the consumption of blends of ethanol above 10
percent. This includes the effect of higher ethanol blends on passenger vehicles and smaller
engines, as well as the impact on infrastructure such as pipelines, storage tanks, and fuel
dispensers. Note that we do not present a comprehensive review of all of the barriers to
uptake of higher ethanol blends. For instance, most car warranties do not cover the use of
blends above E10. In addition, higher ethanol blends and related equipment may cost more
than E10, and corn ethanol has been criticized by some experts and stakeholders for
increasing food prices and for having negative impacts on the environment. This study does
not consider these areas and instead focuses only on technology issues that must be
addressed for the consumption of higher blends of ethanol.
Vehicle Compatibility
The primary technical concerns with using intermediate blends of ethanol in vehicles
include: reduced fuel economy due to the lower energy density of ethanol; increased
emissions of pollutants such as nitrogen oxides (NOx) due to higher catalyst temperatures;
corrosion of metals and other materials in engines and fuel systems; degradation of
elastomers, polymers, and seals, which can lead to fuel leaks; and phase separation of
water and ethanol from gasoline.
Given that the energy density of ethanol (the amount of energy in one gallon of fuel) is
about one-third lower than the energy density of gasoline, cars drive fewer miles per gallon
(mpg) when operating on ethanol blends compared with unblended gasoline. As such,
existing cars driving on higher blends of ethanol will experience range reduction for a given
fuel tank size. Fuel tanks could be made larger in new vehicles to partially address this
problem, but there is no way to directly offset the lower energy density of ethanol compared
with gasoline.
Technical Barriers to the Consumption of Higher Blends of Ethanol
5There are theoretical reasons to be concerned that cars operating on higher ethanol blends
than they were designed for could emit greater concentrations of pollutants in their exhaust
gas. Cars need oxygen from air to combust gasoline, and under normal operation this ratio
of air/fuel is carefully controlled so that the fuel burns optimally. If the ratio is not adjusted
when using ethanol blends, the exhaust temperature will rise and, over time, can result in
deterioration of the catalytic converter. This situation can increase the level of certain
pollutants in the vehicle’s exhaust. Modern cars have the ability to prevent this imbalance
by automatically adjusting the air/fuel ratio depending on the ethanol content of the fuel.
Older vehicles, however, as well as many motorcycles, lawn mowers, and other off-road
equipment, do not have a mechanism for automatically adjusting the air/fuel ratio, which
can pose a problem as described in more detail below.
Ethanol blends are associated with higher emissions of the toxic substances formaldehyde
and acetaldehyde, but their combustion produces lower levels of benzene and the
carcinogen 1,3-butadiene. These blends can also be expected to result in lower emissions of
particulate matter (PM), although PM emissions from gasoline vehicles are already
extremely low.
There are also concerns that higher blends of ethanol could increase evaporative emissions,
or emissions of evaporated, unburned fuel, because ethanol blends have a higher vapor
pressure than gasoline at low to mid concentrations. However, given that E10 has the
highest vapor pressure of any blend level, it is not expected that increasing the ethanol
content of fuel above E10 will result in higher evaporative emissions.
Claims that E15 cannot be safely used in newer (2001 and later) vehicles focus primarily
around a set of studies by the Coordinating Research Council (CRC). Although the CRC
reported leaks and other problems in some vehicle tests, overall most other studies have
found that E15–E30 causes only slight damage to vehicle components. There is little
evidence that these low-intermediate ethanol blends damage metals, and E15 does not
appear to affect plastics, polymers, and similar materials differently than E10. Taking all of
these studies together, we conclude that vehicles model year 2001 or later can safely
consume E15, provided warranty issues can be managed. Although there is some evidence
showing vehicles older than 2001 can tolerate ethanol blends up to E30, these vehicles do
not have the same technological advantages as newer cars, and it is likely not prudent to
use higher ethanol blends in them, even ignoring warranty issues. FFVs that can operate on
E0–E85 are currently being produced at high volume (17 percent of all U.S. car sales in
2011), and non-FFV vehicles can be retrofitted at moderate cost.
Finally, given that ethanol readily mixes with both gasoline and water, water can become
incorporated in the fuel blend. If water contamination is high enough, the ethanol/water mix
will separate from the gasoline and form a layer at the bottom of the tank, in a process
known as phase separation. In general, it is not expected that water contamination with
ethanol blends will be high enough to cause problems with vehicle operation. The risk of
phase separation can be reduced by the addition of solubility improvers.
Technical Barriers to the Consumption of Higher Blends of Ethanol
6Small Engines and Off-road Applications
Equipment with small gasoline engines, such as lawnmowers, snowmobiles, and small
boats, have more serious compatibility issues with higher ethanol blends. New equipment of
these types can be designed to operate on higher ethanol blends, but retrofitting existing
equipment is not likely to be practical. The possibility of replacing lead additives with
ethanol in aviation gasoline for small aircraft should be studied further. Large aircraft and
ships use different types of fuel, and while some types of biofuel can be blended into
aviation fuel, ethanol cannot be used in these applications.
Infrastructure
Fueling infrastructure may have material incompatibility with ethanol, especially with regard
to elastomers.1 Still, there is evidence that E15 may be safely used with some existing fuel
dispensers and pipelines that have been delivering E0 or E10, provided they are cleaned of
all fuel and residual fluids before higher ethanol blends are introduced. Technology is
available for the production of new dispensers, storage tanks, and pipelines that can
accommodate ethanol blends E15–E85, and many existing infrastructure elements can be
retrofitted for this purpose. At the same time, stations offering higher ethanol blends will
still need to offer E0 or E10 for older vehicles and small engines, and a system to minimize
the risk of misfueling must be developed.
Timeline for Consumption of Higher Blends of Ethanol
This review also considers the amount of time needed to make necessary technological
changes to vehicles and infrastructure in order to consume higher blends of ethanol. These
timelines, in addition to solutions for the potential problems discussed above, are
summarized in Table 1.
Technical Barriers to the Consumption of Higher Blends of Ethanol
7Table 1. Summary of technical barriers to using higher blends of
ethanol, potential solutions to those barriers, and timeframe
necessary for technical solutions. This timeline does not consider
non-technical barriers.
Timeframe
for resolving Timeframe for
Solution for
Solution for technical resolving technical
Equipment Problem use of E25-
use of E10-E20 barriers barriers only,3 for E25-
E85
only,2 for E85 use
E15-E20 use
Vehicles Reduced range No solution No solution
from fuel
economy loss
Increased Avoid fueling older Increase No time needed About 5 years
temperatures vehicles with E15- production of new
and pollutants in E20; post-2000 FFVs; retrofit
exhaust vehicles likely other vehicles
compatible
Material Avoid fueling older Increase No time needed About 5 years
incompatibility vehicles with E15- production of new
and leaks E20; post-2001 FFVs; retrofit
vehicles likely other vehicles
compatible
Phase separation No problems likely No problems No time needed No time needed
likely; Can add
solubility
improvers to fuel
Motorcycles, Increased New vehicles and Not clear there is Several years Not advised to fuel these
boats, and small temperatures machines can be a practical for machine vehicles and machines on
engines and pollutants in designed for E15- solution turnover ethanol in near-term
exhaust; 20; existing
material vehicles and
incompatibility machines should
not use higher
ethanol blends
Fuel dispensers Material Some newer Retrofit or replace No time for Hours to days for retrofits; 1-
incompatibility dispensers can use dispensers some existing 2 years for misfueling system
E15; retrofit dispensers;
others; hours to days
development of a for retrofits; 1-2
system to minimize years for
risk of misfueling misfueling
system
Fuel storage tanks Material Retrofit and clean Retrofit or replace Days Days to months
incompatibility tank
Pipelines Corrosion of Possibly no Add liners to No time to Months to 3 years
steel and other modifications inside of pipeline several days
material needed for E15; for and inhibitors to
incompatibility E20, add inhibitors fuel; build new
pipelines
Water Clean pipeline and Clean pipeline Days Days
contamination check seals and check seals
Technical Barriers to the Consumption of Higher Blends of Ethanol
8Finally, we present two hypothetical scenarios of the future consumption of higher blends of
ethanol (ignoring non-technical challenges), in which:
1. E15 increases to 100 percent of gasoline consumed in 2022 (the “E15 in 2022”
scenario); or
2. E85 rises to 25 percent of all gasoline consumed in 2022, and the remaining 75
percent of consumption becomes E15 by 2022 (the “25 percent E85 in 2022”
scenario).
These two consumption scenarios are then evaluated with regards to how they may or may
not satisfy two projections of RFS2 mandated volumes: revised and original. The analysis
finds that if the cellulosic volumes in the RFS2 continue to be revised downward (the
“revised” mandate), the RFS2 could be approximately met from 2016–2022 through the
“E15 in 2022” scenario, and could be fully met (and in fact exceeded) from 2015–2022
given consumption in the “25 percent E85 in 2022” scenario. The RFS2 mandate as
originally set in the statute (the “original” mandate), which calls for 36 billion gallons of
biofuel to be consumed in 2022, could be satisfied from 2017–2022 by the levels in the “25
percent E85 in 2022” scenario, but not at any time by the “E15 in 2022” scenario. As a
comparison with these scenarios and mandated levels, we also present a “repealed”
projection where E10 consumption remains constant (in proportion to overall gasoline
demand) through 2022.
It is important to note that significant other barriers exist to the uptake of higher ethanol
blends, and the analysis here does not demonstrate whether these scenarios of ethanol
consumption are realistically achievable. Current trends of rollout of ethanol-compatible
vehicles and infrastructure have been much slower.
Overall, this study finds that technical barriers do not stand in the way of implementation of
the RFS2 to 2022. At the same time, we did not consider the future production potential for
ethanol or a myriad of other issues such as cost, politics, and negative impacts on food
prices and the environment.
Technical Barriers to the Consumption of Higher Blends of Ethanol
9Introduction
U.S. federal and state policies, regulations, and incentives have promoted the use of ethanol
in road fuel for decades. The current phase of ethanol support began with the Reformulated
Gasoline (RFG) program mandated in 1990, which required a certain oxygen content in
gasoline to reduce pollution in vehicle exhaust.4 At first, this requirement was largely met
by blending gasoline with methyl tertiary butyl ether (MTBE). Following cases of
groundwater contamination by MTBE in the early 2000s, ethanol has become the primary
oxygenate for U.S. gasoline. Then, the Energy Policy Act of 2005 (EPACT05) created the
Renewable Fuel Standard (RFS). The first phase of the RFS, now referred to as RFS1,
mandated 4 billion gallons of renewable fuel to be blended into gasoline in 2006, and 7.5
billion gallons (or about 6 percent of gasoline by volume) in 2012. The RFS1 was amended
and extended in 2007 with the Energy Independence and Security Act (EISA), becoming the
RFS2. The RFS2 split biofuel into four categories, defined by feedstock and by the required
greenhouse gas reduction compared with gasoline or diesel, and mandated volumes in all
categories increase over the duration of the RFS2 (2010–2022).
To date, the majority of biofuel used for compliance with the RFS2 has been ethanol
produced from corn and (to a lesser extent) Brazilian sugarcane. In 2013, the RFS2
mandated the consumption of 16.55 billion gallons of renewable fuel in total; this requires
blending approximately 9.6 percent biofuel (mostly ethanol) in road fuel.5 Some U.S. states
mandate higher blending of ethanol than would be required to comply with RFS2; for
example, all gasoline sold in Minnesota is required to be E20 starting in 2015.6,7 Before
2010, 10 percent ethanol in gasoline (E10) was set as the limit by the Environment
Protection Agency (EPA) for the maximum blend of ethanol that could be used in unmodified
road vehicles without risking compromising operation and performance. EPA has since
issued waivers to allow the use of 15 percent ethanol in gasoline (E15) in vehicle models
introduced in 2001 and later, based on tests showing E15 does not damage these
vehicles.8,9 However, this ruling has faced opposition from the oil and automotive industries,
among other stakeholders, due to concerns that E15 could damage vehicle engines and
other components.10,11 Furthermore, granting a waiver for E15 does not address the need to
provide a dual-stream refueling infrastructure, with E15 for newer vehicles and E10 or
straight gasoline (E0) for older vehicles and small engines.
This study aims to identify the technical barriers to using ethanol blends above E10 and
possible solutions to those barriers. It provides a broad overview of the risk of damage from
using E15 and higher ethanol blends in cars, in other vehicles and non-road equipment
running on smaller gasoline engines, as well as in fueling infrastructure such as pipelines,
storage tanks, and gasoline dispensers. It identifies the technical changes that would be
required in each of these areas to safely use ethanol blends of 15–85 percent. Lastly, it
discusses the amount of time needed to make necessary technological changes to vehicles
Technical Barriers to the Consumption of Higher Blends of Ethanol
10and infrastructure in order to consume higher blends of ethanol and compares this timeline
with projections of RFS2 implementation.
Technical Barriers to the Consumption of Higher Blends of Ethanol
11Vehicle Compatibility
Before approving the use of E15 in newer vehicle models, EPA worked with the U.S.
Department of Energy (DOE)12 to test the effects of E15 on vehicle components.13 A number
of studies on the effects of E15–E30 have also been published by other parties. The primary
technical concerns with using intermediate blends of ethanol in vehicles include:
• reduced fuel economy due to the lower energy density of ethanol;
• increased emissions of pollutants such as NOx due to higher catalyst temperatures;
• corrosion of metals and other materials in engines and fuel systems;
• degradation of elastomers, polymers, and seals, which can lead to fuel leaks; and
• phase separation of water and ethanol from gasoline.
Fuel Economy With Ethanol Blends
Cars drive fewer miles per gallon (mpg) when operating on ethanol blends compared with
unblended gasoline. This is expected because ethanol has about one-third lower energy
density (amount of energy in one gallon of fuel) than gasoline. Studies have generally found
that the fuel economy loss with ethanol blends is consistent with their lower energy
density—that is to say, cars will drive the same distance per unit of energy when running on
gasoline or ethanol blends.14,15,16 Existing cars driving on higher blends of ethanol would
thus experience range reduction for a given fuel tank size. Fuel tanks could be made larger
in new vehicles to partially address this problem with higher ethanol blends,17 but there is
no way to directly offset the lower energy density of ethanol compared with gasoline.
Tailpipe emissions of carbon dioxide (CO2) from the combustion of ethanol and gasoline are
similar on an energy basis, and so using ethanol does not affect a vehicle’s tailpipe CO2
emissions per mile driven. EPA has investigated the potential that cars running on E30 could
be more efficient on an energy basis if their engines are designed for that fuel mix.18,19
However, such vehicles would not achieve these efficiency gains if designed for E30 and
fueled with lower ethanol blends. They would also experience reduced performance or
possibly detonation, a problem caused when the fuel mixture combusts prematurely; this
can damage engines.
Effects of Ethanol on Car Emissions
There are theoretical reasons to be concerned that cars operating on higher ethanol blends
than they were designed for could emit greater concentrations of pollutants in their exhaust
gas. Cars need oxygen from air to combust gasoline, and under normal operation, this ratio
of air/fuel is carefully controlled so that the fuel burns optimally. In the cylinder where
Technical Barriers to the Consumption of Higher Blends of Ethanol
12combustion takes place, the fuel evaporates before it is burned, and this evaporation helps
cool off the air/fuel mixture and exhaust gas. Ethanol contains oxygen in its molecular
structure (while gasoline does not), and so requires less air for combustion per unit fuel; in
other words, the optimal air/fuel ratio for ethanol blends is lower than for pure gasoline. If
the same air/fuel ratio for gasoline is used for ethanol blends, there will be too much air for
the amount of fuel in the cylinder—this is called “enleanment.”20 In this situation, there is
not enough fuel evaporation to cool the mixture, and the temperature of the exhaust gas
rises.21 This raises temperatures inside the catalytic converter,22 and over time, this can
accelerate catalyst deterioration. In addition, excess oxygen in the exhaust can inhibit
proper functioning of the catalytic converter, which converts NOx into stable nitrogen and
oxygen gases. To summarize, enleanment from using high-oxygen fuels like ethanol can
theoretically lead to overheating of the catalytic converter and to increased emissions of
harmful pollutants.
Modern cars have the ability to prevent enleanment by adjusting the air/fuel ratio
depending on the ethanol content of the fuel. There is an oxygen sensor on the exhaust line
in between the engine and the catalytic converter (Figure 1). If the sensor detects elevated
oxygen in the exhaust, indicating enleanment, it sends a signal to the fuel injector to
decrease the air/fuel ratio. This keeps the catalytic converter operating at the right air/fuel
conditions. Vehicle systems with an oxygen sensor are referred to as “closed loop,” whereas
those without control over the air/fuel ratio are referred to as “open loop” systems. Since
2001, U.S. cars have been equipped with more accurate oxygen sensors capable of
correcting the air/fuel mixture relatively quickly, while in older cars (1981–2000),23 simpler
oxygen sensors take a longer time to adjust.24 All cars made in 1981 and after have closed
loop systems.25 Modern vehicles will still always operate under open loop conditions when in
full throttle or during a cold start.26 Older vehicles, as well as many motorcycles, lawn
mowers, and other off-road equipment, are open loop and do not have a mechanism for
automatically adjusting the air/fuel ratio; this is discussed in more detail in the sections
below on small engines and non-road vehicles.
Technical Barriers to the Consumption of Higher Blends of Ethanol
13Figure 1. Diagram of vehicle components, showing placement of
engine, oxygen sensor, and catalytic converter. Image by the
International Council on Clean Transportation.
ENGINE%
Some studies have measured temperature increases in the exhaust gas and catalytic
converters of cars, both pre-2001 and post-2001, operating on E15 or E20 when under open
loop conditions (i.e., without feedback from the oxygen sensor), compared with emissions
when operating on pure gasoline.27,28,29 The studies found slightly higher emissions of NOx
and lower emissions of carbon monoxide (CO) and unburned hydrocarbons in vehicles
operating on E15 or E20 compared with those using E0.30,31 One study showed that under
closed loop (normal) conditions, the exhaust temperature did not increase with higher
ethanol blends;32 this is as expected given that the oxygen sensor adjusts the amount of
fuel delivered to maintain the same air/fuel ratio in closed loop operation. In a highly
publicized study by the Coordinating Research Council (CRC),33,34 out of seven vehicles
tested,35 one failed emission standards on E15, but a duplicate vehicle passed on E15 and
both passed using E20. In an Australian study, one vehicle produced higher NOx emissions
at high mileage on E20 compared with E0, and this was attributed to higher catalyst
temperatures over time.36 Interestingly, another study reported no change in emissions with
vehicles model year 1985–1998 when operating on E30 under closed loop conditions,
although this study did note these older cars required a half-hour of driving before the fuel
injector fully adjusted to the ethanol content of the fuel, which may be expected with the
first-generation oxygen sensors used in this vehicle age class.37 Older vehicles (pre-1980s)
that have no air/fuel control may be incompatible with even E5.38
Ethanol blends are associated with higher emissions of the toxic substances formaldehyde
and acetaldehyde,39,40,41,42 but they produce lower levels of benzene and the carcinogen 1,3-
butadiene. Using California’s relative toxicity factors, one study calculated that the overall
toxicity of emissions from ethanol blends was lower than for gasoline.43 All ethanol blends
can also be expected to result in lower concentrations of PM in the exhaust gas than
Technical Barriers to the Consumption of Higher Blends of Ethanol
14gasoline,44 and PM is associated with lung and heart disease.45 On the other hand, PM
emissions from gasoline vehicles are already extremely low.
There are also concerns that higher blends of ethanol could increase evaporative emissions,
or emissions of evaporated, unburned fuel from the fuel tank and from joints and seals
along the fuel line, because ethanol blends have a higher vapor pressure than gasoline at
low to mid concentrations. For example, the CRC reported higher evaporative emissions in
fuel systems with 5.7 percent ethanol compared with pure gasoline.46 However, E10 has the
highest vapor pressure of any blend level; vapor pressure decreases with ethanol content
thereafter. E15 and E20 have slightly lower vapor pressure than E10, and E85 has a vapor
pressure significantly lower than E10 or gasoline.47,48,49 Thus, it is not expected that
increasing the ethanol content of fuel above E10 will result in higher evaporative emissions.
Ethanol Effects on Materials and Fuel Leaks
Ethanol is more corrosive than gasoline because it contains more dissolved oxygen, and this
has led to concerns that ethanol blends above E10 could damage materials in car engines
and fuel systems. Ethanol damage to materials could potentially lead to leaks or fuel filter
blockage, especially in older vehicles.50 Partly for these reasons, most car warranties in the
United States only cover usage of E0–E10.51
Metals used in engines and other vehicle parts have generally not been found to be
susceptible to corrosion by low to mid blends of ethanol. In a review of the literature, the
National Renewable Energy Laboratory (NREL)52 reported slight and insignificant corrosion
of vehicle metals with E10 and E20, even when testing with an “aggressive” ethanol blend
representing the “worst case” contaminated fuel that could potentially be found on the
market. The Australian study mentioned above found slightly greater wear on some metallic
engine components in a few vehicles operating on E20 vs. E0, with no effect on
performance.53 Other studies on legacy vehicles found no effect of E15,54,55 E20,56 or E3057
on engine materials or other metal parts.
Ethanol may also affect elastomeric components (elastic polymers, or rubber- and plastic-
like materials) in vehicles by changing their dimensions and by reacting with the material.58
However, an NREL review found that elastomer properties changed when exposed to E10
versus E0, but that there was no difference in properties when comparing E15 with E10.59
As with metals, studies on legacy vehicles (model years 1994–2001) did not observe any
degradation of elastomers, polymers, or any other materials with E1560,61 or E20.62
While the CRC study on engine durability63 did not specifically measure changes in materials
with exposure to ethanol, it did report leakage from engines in two vehicles operating on
“aggressive” E15, and four out of seven vehicles at “aggressive” E20, leading to engine
failure in two (although duplicates of some of these vehicles passed). These results were
downplayed in a review by NREL64 because of the small sample size and statistically
insignificant results. Indeed, the CRC study reads, “[S]ince this study was designed for
Technical Barriers to the Consumption of Higher Blends of Ethanol
15scoping purposes, the findings should only be used to identify where additional testing
should be performed” (p. 12).
NREL also criticized CRC’s use of the leakdown test,65 because there is no agreed threshold.
However, the leakdown test is very robust, and we do not consider this criticism to be valid.
It would be similar to claiming the SAT is not a useful test because there is no particular
score that indicates failure. The CRC study also identified problem areas in various
components of the fuel system (fuel pump seals, filler hoses, fuel level senders, and
valves). On the other hand, the CRC did not find any negative impacts from soaking fuel
pumps in “aggressive” E20,66 and other studies have reported no leaks in legacy vehicles
operating on E15,67,68 E20,69 or E30 in vehicles model years 1985–1999.70 In addition, a
study at the University of Minnesota reported no problems caused by ethanol when a large
number of vehicles were driven on E20 under normal conditions, although it should be
noted this study did not test for deterioration under high-mileage or stressful conditions.71
Apart from the small sample size, it is not clear why leakage was observed in the CRC study
but not in the others cited here.
Although the CRC reported leaks in some vehicle tests, overall most studies have found that
E15–E30 causes only slight damage to vehicle components. There is little evidence that
these low-intermediate ethanol blends damage metals, and E15 does not appear to affect
plastics, polymers, and similar materials differently than E10.
Phase Separation of Water and Ethanol from
Gasoline
Gasoline typically contains small amounts of water contamination, but since gasoline and
water don’t mix with each other, the water stays at the bottom of the fuel tank. Ethanol, on
the other hand, readily mixes with both gasoline and water, and allows water to become
incorporated in the fuel blend. If water contamination is high enough, the ethanol/water mix
will separate from the gasoline, forming a layer at the bottom of the tank—this is “phase
separation.”72 The fuel line is at the bottom of the tank, and so a high concentration of
water/ethanol may be drawn out and cause problems starting the car.73 However, phase
separation only occurs at relatively high concentrations of water74,75,76 and generally is not a
major concern. The risk of phase separation can be reduced by the addition of solubility
improvers.77
Flex-Fuel Vehicles (FFVs)
FFVs are designed to be able to run on pure gasoline or on ethanol blends up to E85.78 FFVs
are popular in Brazil, and their market share in the United States has grown in recent years.
Given that it’s just as easy to make FFVs that can operate on all blends of ethanol up to E85
as to engineer vehicles that have an ethanol limit greater than E20 but less than E85, we do
not consider the latter category here.
Technical Barriers to the Consumption of Higher Blends of Ethanol
16FFVs are not much different from regular cars, and it’s relatively easy and inexpensive to
produce an FFV instead of a regular car. Several relatively minor technical adjustments are
required, including replacing or coating certain metal and elastomeric components,
increasing the fuel system capacity to account for the lower energy density of ethanol, and
installing a sensor in the fuel line that measures alcohol concentration.79 FFVs can run on
pure gasoline or any blend of ethanol up to E85 and generally operate the same as
conventional vehicles. Non-FFVs can also be retrofitted to become flex-fuel and retrofit kits
are available, although such conversions may be expensive for the consumer and care must
be taken to ensure the converted vehicle still meets emission regulations.80 In addition, FFV
conversions must be done by a certified technician, or the owner may lose the vehicle
warranty.
The main downside to FFVs is the cost; new FFVs cost $70–100 more to manufacture than a
non-FFV of the same vehicle model.81,82 While this additional cost is small compared with
the purchase price of a new vehicle, it adds up for the manufacturer when considering all
vehicles produced in a year. In addition, changes must be made to the assembly line, which
presents an upfront cost. Through 2016, automakers receive additional credits from selling
FFVs to comply with EPA’s greenhouse gas standards83 and receive credits through 2019 for
complying with the National Highway Traffic Safety Administration’s fuel economy
standards. For these reasons, a rapidly growing proportion of vehicle sales are FFVs; in
2011, 17 percent of all cars sold in the United States were FFVs,84 and GM has pledged that
half of its new cars sold in 2015 will be FFVs.85 But many FFV owners are not aware they
have an FFV,86 and consumption of E85 has been very low. Table 2 shows capacity of the
U.S. FFV fleet to consume E85 compared with actual E85 consumption; on average, only
about 1 percent of the average FFV’s fuel consumption is E85.
Technical Barriers to the Consumption of Higher Blends of Ethanol
17Table 2. FFV consumption of E85 fuel, vehicle population, and
percent E85 usage
ANNUAL ANNUAL E85
E85 FUEL E85 FFV VEHICLE
VOLUME OF CONSUMPTION BY
CONSUMPTION87 POPULATION88
YEAR E85 USE FFVS, AS % OF
(MILLION (MILLION
(GALLON TOTAL FFV FUEL
GALLONS) VEHICLES)
E85/FFV) CONSUMPTION89,90
1998 2 0.1 12.3 1.4%
1999 4 0.5 8.9 1.0%
2000 12 0.9 13.7 1.6%
2001 15 1.4 10.9 1.3%
2002 18 2.1 8.8 1.0%
2003 26 2.8 9.3 1.1%
2004 32 3.4 9.2 1.1%
2005 38 4.1 9.2 1.1%
2006 44 5.1 8.7 1.1%
2007 54 6.2 8.8 1.1%
2008 62 7.3 8.6 1.1%
2009 71 8.4 8.5 1.1%
91
2010 90 9.7 9.3 1.1%
There are several possible reasons behind the low consumption of E85. E85 is generally
more expensive than gasoline on an energy basis,92 so it costs more per mile. For example,
one gallon of a mixture of 80 percent ethanol and 20 percent gasoline has 73 percent of the
energy content of pure gasoline and 74 percent of the energy content of E10. If a fueling
station sells E10 for $3.00 per gallon, E85 should be priced at $2.23 per gallon for an
equivalent price per mile. In practice, E85 is often sold only about 10 percent cheaper than
E10 on a volume basis;93 $2.70 in this example. An FFV owner looking to minimize refueling
costs in this market would keep fueling with E10 because it’s cheaper per mile driven. The
lower energy density of ethanol also means that a consumer cannot drive as far on a tank of
E85, and must refuel more often than they would if using E10. Considering this
inconvenience, it is likely that E85 would need to be priced even lower (perhaps $2.00 per
gallon in this example) to attract consumers. Note that, as described above, CO2 emissions
are similar for ethanol and gasoline on an energy-equivalent basis, and so these differences
in energy density are not significant from a climate perspective.
Another important factor in the low consumption of E85 is a geographical mismatch
between location of FFVs and fueling stations offering E85. As an analysis from Iowa State
University shows, most E85 is offered in the Midwest, while Texas, California, and the
Southeastern United States have large numbers of FFVs with no access to high ethanol
fuel.94 Finally, some drivers may simply be resistant to using a different fuel or may even
fail to realize that they are driving FFVs.
Technical Barriers to the Consumption of Higher Blends of Ethanol
18Small Engines and
Off-road Applications
Equipment With Small Gasoline Engines
Equipment with small engines—including lawnmowers, snowmobiles, hand-trimmers, and
other tools—typically operates with open loop systems (i.e., no systematic air/fuel
adjustment) and is designed to deliver a rich fuel mixture (low air/fuel ratio, the opposite of
enleanment). The evaporative cooling of the extra fuel helps keep the engine from
overheating and prolongs the life of the equipment.95
Most manufacturers of equipment using small engines permit usage of ethanol blends up to
E10 under warranty.96 Because these systems cannot adjust the air/fuel ratio, enleanment
is a major concern. Tests by NREL confirmed that enleanment did occur in several types of
equipment with small gasoline engines, leading to significant increases in exhaust
temperature when operating on E15 compared with E0 (10–50°F) and with E20 compared
with E0 (20–70°F).97 However, the exhaust temperature was only 5–10°F higher when
comparing E15 operation with E10, suggesting that the most pronounced effect of ethanol
on exhaust temperature occurs between E0 and E10. Like most of the vehicle tests
discussed in the previous section, NREL’s test on small engines found only slight changes in
emissions, with NOx increasing and hydrocarbons/carbon monoxide decreasing with higher
blends of ethanol.
A more serious problem is that three handheld trimmers in this study experienced
unintentional clutch engagement when operating on higher ethanol blends. Because
equipment with small engines typically run on a rich fuel mixture, enleanment from ethanol
can actually lead to more efficient combustion and higher power than when operating on
pure gasoline. In the case of the handheld trimmers, the resulting higher idle speed forced
the clutch to engage and turned on the equipment. This effect could be dangerous if it
occurred in some types of equipment, such as chainsaws. Too much enleanment could also
98
lead to misfire, and thus higher ethanol blends increase the chances that misfire may
occur under some operating conditions for equipment with a tight operating tolerance.
Enleanment in small engines can be addressed to some extent by adjusting the choke to
reduce the amount of air that is admitted into the engine or by using larger carburetor jets
to increase the amount of fuel delivered; either of these changes would help lower the
99
air/fuel ratio. It is unlikely, and unadvisable, that owners would make these adjustments
on existing equipment, but new equipment could potentially be designed to safely operate
on higher blends of ethanol if desired. Such new equipment may, however, have higher
Technical Barriers to the Consumption of Higher Blends of Ethanol
19hydrocarbon and carbon monoxide emissions if the small engine is fueled with gasoline or
E10 instead of the higher ethanol blend for which it was designed.
As with cars, higher ethanol blends could damage materials that were not designed for
them. However, in the NREL study no negative effects on materials were observed. Most of
these engines have a short service life, in terms of hours of use, which also minimizes the
impacts of material damage. In principle, materials damage to equipment and vehicles with
small engines should not differ from that in cars because in both cases the fuel lines and
other components are exposed to ethanol most of the time, whether in operation or not.
Motorcycles
Because emission standards for motorcycles are less strict than for cars, not all motorcycles
are equipped with catalytic converters, and some motorcycles have a more basic type of
catalytic converter that does not require accurate oxygen sensors and systematic
adjustment of the air/fuel ratio. Fifty-eight percent of motorcycle models for 2014 operate
on an open loop system, and almost half of these are open loop with multiple cylinders.100
NREL reported that equipment with multiple cylinders experienced more severe problems
with enleanment because, in some cases, the cylinders experienced different air/fuel
ratios.101 For the approximately 40 percent of motorcycle models with closed loop systems,
fueling on E15 or E20 should not carry a significant risk for overheating or increased
emissions, although materials compatibility could still be an issue. Because many
motorcycle owners probably don’t know if their vehicle has a closed loop system or not, in
general it is advisable for motorcycles to avoid fueling on higher blends of ethanol. While
refueling with E10 probably does lead to enleanment in some motorcycles, the effect is
likely small enough not to result in serious problems.
Aviation and Marine
Commercial ships and aircraft do not use gasoline, and so there is little potential for uptake
of ethanol blends in these sectors over the near to medium term. Instead of ethanol, there
is the potential for “drop-in” biofuels102 to be blended with jet fuel (a kerosene-based fuel
somewhat similar to diesel). In this case, because the biofuel must be chemically similar to
jet fuel, blending should not create any problems. Commercial ships typically operate on
bunker fuel (an inexpensive and dirty petroleum derivative) and because low fuel cost is
very important to shipping, this sector has not yet made any significant steps toward
increased blending of biofuels with marine fuel.
Some small recreational boats have gasoline engines. Because these tend to have open loop
control, enleanment is a problem, as in small engines and older vehicles. Testing E15 at
wide open throttle, when enleanment is most likely to occur, NREL observed enleanment,
high temperatures in the exhaust and catalyst, and degradation of metals, elastomers, and
valves in small boats, compared with use at E0.103 In an Australian study, some small boats
stalled when operated on E10 and E20.104 These results indicate that E15 and E20 should
Technical Barriers to the Consumption of Higher Blends of Ethanol
20not be used in small boats, although additional research could be conducted to confirm
these findings. Presumably, new boats could be designed to operate on higher blends of
ethanol, with similar adjustments to the choke and carburetor as described for small
engines, and using ethanol-compatible materials. However, as with small engines, marine
engines designed for higher ethanol blends would have higher hydrocarbon and carbon
monoxide emissions if fueled with gasoline or E10. Also, the constant exposure to water and
humidity in marine applications could exacerbate problems with ethanol adsorption of water,
increasing the risk of phase separation.
Unlike commercial planes, some small personal aircraft do operate on gasoline, called
“Avgas.” Unlike motor gasoline in the United States, Avgas still uses lead additives to boost
the octane rating, and because lead is toxic, some have argued for ethanol to replace lead
as an octane improver in Avgas.105 New aircraft could potentially be designed to
accommodate ethanol blends, and aircraft operating on pure or almost pure ethanol have
already been developed.106,107 However, existing aircraft running on Avgas may have
significant compatibility issues with ethanol, and further research must be conducted before
recommending ethanol blends in small airplanes.
Technical Barriers to the Consumption of Higher Blends of Ethanol
21Infrastructure
In order to supply higher blends of ethanol to vehicles, compatible infrastructure must be in
place. Here, we discuss the effects of ethanol on fuel dispensers, storage tanks, and
pipelines. We also describe available technologies that can be used to adapt infrastructure
to the supply of E15–E85.
Fuel Dispensers
Concern about using E15 with existing fuel dispensers centers around materials
compatibility. An Oak Ridge National Laboratory (ORNL) study tested the effects of
“aggressive” (i.e., contaminated) ethanol blends from E10–E25 on dispenser materials.108
They found very little corrosion of metallic components with soaking in “aggressive” E10,
E17, and E25, and higher ethanol blends were not associated with greater corrosion. When
elastomers were soaked in fuel, they swelled, even with pure gasoline.109 This swelling was
greater in ethanol blends and some elastomers softened, indicating a reaction with the
ethanol. The highest swell occurred with soaking in E10 or E17, with less swelling at E25,
suggesting potential damage may be greatest at lower blends of ethanol. Some of these
elastomers have a flexible design, and new components could be made that are ethanol-
compatible. Sealants leaked with E10 and E25, but simply wrapping the seals with Teflon
tape was effective at preventing leaking.
Gilbarco, a major manufacturer of fuel dispensers, covers use of E15 under their warranty
for new products and even retroactively extended this coverage to all dispensers sold since
2008.110 This suggests that new dispensers, at least with this manufacturer, are already
using materials compatible with E15, and it indicates an opportunity for some fueling
stations with dispensers five years old or less to offer E15 immediately.111 On the other
hand, Underwriter Laboratories (UL), a major certification body for fueling infrastructure,
only covers regular dispensers with the use of fuel up to E10 at this point,112 and
certification may be required by law for fuel dispensers, depending on location. So even
though some existing dispensers may be able to handle E15, it is unlikely that many fueling
station owners will supply E15 without modifications unless UL extends its certification for
E10 dispensers to E15. UL has a separate certification available for dispensers designed for
E25 or E85. Additional research would be required to determine whether regular dispensers
produced today are compatible with blends higher than E15.
It is relatively inexpensive to retrofit existing dispensers for station owners with dispensers
that are not currently warrantied for the use of higher blends of ethanol. Gilbarco sells a
retrofit kit for $1,800 that allows use of blends up to E25.113 Other estimates of retrofit cost
are in the ballpark of $1,000–$4,000.114
Technical Barriers to the Consumption of Higher Blends of Ethanol
22Stations offering E15 would also need to offer E10 or E0 for older vehicles, motorcycles,
small boats, and equipment with small engines. This will require a system to be put in place
to reduce the risk of people accidentally using the wrong type of fuel; at a minimum, that
would involve a campaign of driver education and a clear system of labeling to discourage
misfueling.
Use of ethanol blends above E25 requires retrofitting or installing new dispensers; both of
these options are available, but are more expensive than retrofitting dispensers for use with
E15–E25. In addition, it is likely that the fuel station owner would have to replace or retrofit
their fuel storage tanks (discussed in the next section). From a survey and literature review,
NREL determined that the cost of retrofitting both the storage tank and dispensers for E85
would be around $11,000 per station, and replacing these parts with E85-compatible
equipment would cost around $59,000.115 If stations are to offer both E10 and higher
ethanol blends, they may require additional storage tanks rather than just replacing existing
ones, increasing the cost. Thus, although the technology for dispensing high-ethanol fuel is
available, the conversion cost may discourage fuel station owners from offering E85. This
cost is partially offset by a federal investment tax credit for the installation of E85 fueling
equipment that is set to expire at the end of 2013.
Underground Storage Tanks (USTs)
Little research has been conducted specifically on the effects of ethanol on USTs. A second
study by ORNL116 relied heavily on the previous ORNL study discussed above on dispenser
materials and how ethanol would affect similar materials in USTs. There are potential
problems with steel tanks, and literature reviewed by ORNL suggested corrosion inhibitors
may be necessary to prevent the serious problem of “stress corrosion cracking” (SCC) in
USTs. Other materials also had mixed results. Fiberglass-reinforced plastic was found to
handle E15 well but not E50 or E85. Most flexible plastic piping and elastomers used in USTs
did not experience significant damage with E15. Interestingly, this study found a significant
difference in materials durability between E0 and E10, but not between E10 and E15. This
suggests that some problems with ethanol that may affect USTs have likely already
occurred, but that increasing the ethanol percentage to E15 may not make matters worse.
When preparing for a switch to E15 in existing USTs, it is necessary to first clean out the
tank to minimize water contamination. To handle E85, USTs would probably need to be
more substantially retrofitted or replaced.
Pipelines
Ethanol blends are typically not transported via pipeline in the United States—pure gasoline
is piped, and ethanol is shipped in trucks, and the two are blended together at the
destination. But in the future, greater volumes of ethanol could potentially be transported
by pipeline from the Midwest, where most ethanol is produced, to other parts of the
country. As with USTs, there are serious concerns about ethanol causing SCC in
Technical Barriers to the Consumption of Higher Blends of Ethanol
23pipelines.117,118 Oxygen in ethanol exacerbates corrosion by protecting most of the steel
surface and channeling degradation to isolated areas of steel, and by absorbing electrons
emitted from the steel during corrosion. These problems can be addressed by lining the
pipeline with a protective material or by adding corrosion inhibitors to the fuel.119
Water contamination is also a potential issue with ethanol in pipelines because water
absorbed by ethanol may contain rust and other particulates that accumulate during
transportation of gasoline. The presence of such contaminants can be minimized by cleaning
out a pipeline before transporting ethanol through it.120 In addition, the risk of water
contamination is reduced when ethanol blends are transported regularly, instead of
alternating batches of ethanol blends and pure gasoline. Lastly, filters can be added to
remove contaminants when fuel exits the pipeline.121 According to the Pipeline Research
Council International,122 E15 can be transported through pipelines without any
modifications, and E20 can be transported if corrosion inhibitors are added to the fuel. The
effects of corrosion inhibitors on vehicle emissions and material compatibility should be
investigated before they are used routinely.
There is little research done on the effects of transporting ethanol blends above E20 through
pipelines, but it appears to be possible. Brazil has been transporting pure ethanol through
pipelines since the 1970s. Although some seals and elastomers have had to be replaced,
Petrobras, Brazil’s national oil company, claims they have not experienced SCC in their
pipelines, even without installing liners.123 In the United States, Kinder Morgan has been
transporting alternating batches of ethanol and gasoline in Florida since 2008,124 and
recently has been working on similar projects in other states.125
The U.S. Department of Energy (DOE)126 has considered the feasibility of constructing an
ethanol-only pipeline from the Midwest to the East Coast. Although the cost would be
significant, it would not be prohibitive if demand for ethanol on the East Coast were high
enough. The pipeline would have to transport 4.1 billion gallons of ethanol per year to be
cost competitive, compared with expected demand of 2.8 billion gallons per year. Like all
new pipelines, a dedicated ethanol pipeline would likely face delays from siting, permitting,
financing, and regulation.
Technical Barriers to the Consumption of Higher Blends of Ethanol
24Timeline for Consumption
of Higher Blends of
Ethanol
In this section, we discuss the amount of time needed to make necessary technological
changes to vehicles and infrastructure in order to consume higher blends of ethanol. We
compare this timeline with projections of RFS2 implementation.
Timeline for Technological Changes in Vehicles and
Infrastructure
Vehicles: The major concerns with using higher blends of ethanol in vehicles are increased
emissions, material incompatibility, and phase separation of water and ethanol from
gasoline. The risk of phase separation is limited in general and could be addressed by
adding solubility improvers to fuel. Cars manufactured in 2001 and later have the proper
controls and materials to handle E15 and likely E20 and do not need any modification. At
the time of writing, it is estimated that at least 50 percent of the car fleet is in this age
class, and by 2022, virtually all cars driven in the United States will be capable of operating
on E15.127,128 Many cars manufactured today are FFVs, and other cars could relatively easily
be retrofitted to be flex-fuel. Not accounting for other factors like cost, the U.S. fleet could
theoretically be technologically ready to consume significant amounts of E15 and E85 within
a few years.
Dispensers and tanks: Some current fuel dispensers appear to be compatible with E15,
and it is easy and relatively inexpensive to convert existing dispensers to handle E15–E25.
Gilbarco advertises that this conversion takes only three hours. Retrofitting or replacing
dispensers to be compatible with E85 may take longer, but not likely more than a few days.
A system to minimize the risk of misfueling must be developed. It is difficult to know how
long this would take, as EPA has not proposed such a system yet; for the purposes of the
projections below, we assume that, only considering technical issues, it could be on the
order of one to two years. Some existing underground storage tanks may be compatible
with E15, but to accommodate higher blends would require retrofits or replacements. We
were unable to find estimates of how long it would take to replace these tanks, but assume
it should not be longer than a few months in most circumstances.
Pipelines: Existing pipelines may already be compatible with E15 and may be able to
accommodate E20 if corrosion inhibitors are added to the fuel. To ensure compatibility with
Technical Barriers to the Consumption of Higher Blends of Ethanol
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